  let server = require('express')();
  let mysql = require('mysql');
  const port = 81;

  // 解决跨域
  server.all("*",function(req,res,next){
      //设置允许跨域的域名，*代表允许任意域名跨域
      res.header("Access-Control-Allow-Origin","*");
      //允许的header类型
      res.header("Access-Control-Allow-Headers","content-type");
      //跨域允许的请求方式 
      res.header("Access-Control-Allow-Methods","DELETE,PUT,POST,GET,OPTIONS");
      if (req.method.toLowerCase() == 'options')
          res.send(200);  //让options尝试请求快速结束
      else
          next();
  })

  let sql = mysql.createConnection({
    host     : 'localhost',
    user     : 'root',
    password : '123456',
    database : 'teach'
  });
  
  sql.connect();

  server.get("/firstPage",function(request,response){
    sql.query('SELECT * FROM firstpagelist',function(error,data){
      if(error){
        console.log(error)
        response.send("error")
        return;
      }
      response.send(JSON.stringify(data));
    })
  })



  let id = 0;
  server.get("/click",function(request,response){
    id = request.query.id;
    server.get("/resere",function(request,response){
      sql.query(`SELECT * FROM firstpagelist WHERE id=${id}`,function(error,data){
        if(error){
          console.log(error)
          response.send("error")
          return;
        }
        response.send(JSON.stringify(data));
      })
    })
  })


  server.get("/getol",function(request,response){
    sql.query('SELECT * FROM secondpage',function(error,data){
      if(error){
        console.log(error)
        response.send("error")
        return;
      }
      response.send(JSON.stringify(data));
    })
  })



  server.get("/result",function(request,response){
    id = request.query.id;
    console.log(id);
    server.get("/asked",function(request,response){
      sql.query(`SELECT * FROM secondpage WHERE id=${id}`,function(error,data){
        if(error){
          console.log(error)
          response.send("error")
          return;
        }
        response.send(JSON.stringify(data));
      })
    })
  })


  server.listen(port)
  console.log("server is running at " + port)